Impact of the surrounding ambient temperature on the fresh and hardened properties of one-part alklai-activated materials properties incorporating recycled brick powder and aggregate

Abstract

This study investigates the influence of the combined effect of mixing and curing temperatures on the flowability, slump height reduction, flexural and compressive strengths, water absorption, and microstructural performance of one-part alkali-activated materials (AAM), providing insight into the in situ efficiency and applicability of these materials. The effect of temperature was evaluated for two different mix designs: one prepared with 100% natural aggregates (NA) and the other with 50% brick aggregates (BA). Four different surrounding temperatures were selected: 35, 20, 10, and 0 °C, and the temperatures were varied together at 0, 10, 20, and 35 °C; consequently, the results describe the combined exposure condition and do not isolate the individual effects of mixing temperature and curing temperature. The workability of both mix designs was found to be dependent on the surrounding temperature, with lower flowability and a reduction in slump height as temperature increased. At the same time, increasing the surrounding temperature was found to increase the 3-day strength performance of the mixture. Nevertheless, 28-day mechanical strength performance was better for ambient-prepared mixtures, indicating that high temperature might initially boost AAM performance, but does not allow it to reach its maximum mechanical strength performance at later ages. Similarly, the water absorption capacity of the mixture was found to depend on the surrounding temperature, with the lowest value for the mixture prepared at 35 °C. Scanning electron microscopy (SEM) analysis revealed that aggregates in both mixtures (100% NA and 50% BA) delaminated from the cement paste at 0 °C. The results presented in this study provide an insight into the efficiency and performance of AAM under varying environmental conditions.